Corrections to the Landau hydrodynamical model of multiparticle production due to viscosity

Abstract

We have obtained an analytic solution for the one-particle distribution in the Landau model with viscosity taken into account in three dimensions. The one-dimensional solutions which had previously been obtained by others are discussed together with their validity. The motivation for the present detailed study has been the recent experimental observation of the violation of Feynman scaling in the central region, a feature which had been the prediction of the Landau model. The inclusion of viscosity amounts to a flattening of the central “plateau”. Based on the solution obtained, criteria for the validity of ideal hydrodynamics are derived. These criteria show that for some cases of viscous fluid, the changes from the case of ideal fluid are considerable and have a step-like character. A criticism of the previous attempts to include viscous terms is given.